<?php
/*
 *  $Id: Mysql.php 7490 2010-03-29 19:53:27Z jwage $
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * and is licensed under the LGPL. For more information, see
 * <http://www.doctrine-project.org>.
 */

/**
 * Doctrine_Export_Mysql
 *
 * @package     Doctrine
 * @subpackage  Export
 * @author      Konsta Vesterinen <kvesteri@cc.hut.fi>
 * @author      Lukas Smith <smith@pooteeweet.org> (PEAR MDB2 library)
 * @license     http://www.opensource.org/licenses/lgpl-license.php LGPL
 * @link        www.doctrine-project.org
 * @since       1.0
 * @version     $Revision: 7490 $
 */
class Doctrine_Export_Mysql extends Doctrine_Export
{
	/**
	 * drop existing constraint
	 *
	 * @param string    $table        name of table that should be used in method
	 * @param string    $name         name of the constraint to be dropped
	 * @param string    $primary      hint if the constraint is primary
	 * @return void
	 */
	public function dropConstraint($table, $name, $primary = false)
	{
		$table = $this->conn->quoteIdentifier($table);

		if ( ! $primary) {
			$name = 'CONSTRAINT ' . $this->conn->quoteIdentifier($name);
		} else {
			$name = 'PRIMARY KEY';
		}

		return $this->conn->exec('ALTER TABLE ' . $table . ' DROP ' . $name);
	}

	/**
	 * createDatabaseSql
	 *
	 * @param string $name
	 * @return void
	 */
	public function createDatabaseSql($name)
	{
		return 'CREATE DATABASE ' . $this->conn->quoteIdentifier($name, true);
	}

	/**
	 * drop an existing database
	 *
	 * @param string $name name of the database that should be dropped
	 * @return string
	 */
	public function dropDatabaseSql($name)
	{
		return array(
            'SET FOREIGN_KEY_CHECKS = 0',
            'DROP DATABASE ' . $this->conn->quoteIdentifier($name),
            'SET FOREIGN_KEY_CHECKS = 1'
            );
	}

	/**
	 * create a new table
	 *
	 * @param string $name   Name of the database that should be created
	 * @param array $fields  Associative array that contains the definition of each field of the new table
	 *                       The indexes of the array entries are the names of the fields of the table an
	 *                       the array entry values are associative arrays like those that are meant to be
	 *                       passed with the field definitions to get[Type]Declaration() functions.
	 *                          array(
	 *                              'id' => array(
	 *                                  'type' => 'integer',
	 *                                  'unsigned' => 1
	 *                                  'notnull' => 1
	 *                                  'default' => 0
	 *                              ),
	 *                              'name' => array(
	 *                                  'type' => 'text',
	 *                                  'length' => 12
	 *                              ),
	 *                              'password' => array(
	 *                                  'type' => 'text',
	 *                                  'length' => 12
	 *                              )
	 *                          );
	 * @param array $options  An associative array of table options:
	 *                          array(
	 *                              'comment' => 'Foo',
	 *                              'charset' => 'utf8',
	 *                              'collate' => 'utf8_unicode_ci',
	 *                              'type'    => 'innodb',
	 *                          );
	 *
	 * @return void
	 */
	public function createTableSql($name, array $fields, array $options = array())
	{
		if ( ! $name)
		throw new Doctrine_Export_Exception('no valid table name specified');

		if (empty($fields)) {
			throw new Doctrine_Export_Exception('no fields specified for table "'.$name.'"');
		}
		$queryFields = $this->getFieldDeclarationList($fields);

		// build indexes for all foreign key fields (needed in MySQL!!)
		if (isset($options['foreignKeys'])) {
			foreach ($options['foreignKeys'] as $fk) {
				$local = $fk['local'];
				$found = false;
				if (isset($options['indexes'])) {
					foreach ($options['indexes'] as $definition) {
						if (is_string($definition['fields'])) {
							// Check if index already exists on the column
							$found = $found || ($local == $definition['fields']);
						} else if (in_array($local, $definition['fields']) && count($definition['fields']) === 1) {
							// Index already exists on the column
							$found = true;
						}
					}
				}
				if (isset($options['primary']) && !empty($options['primary']) &&
				in_array($local, $options['primary'])) {
					// field is part of the PK and therefore already indexed
					$found = true;
				}

				if ( ! $found) {
					if (is_array($local)) {
						foreach($local as $localidx) {
							$options['indexes'][$localidx] = array('fields' => array($localidx => array()));
						}
					} else {
						$options['indexes'][$local] = array('fields' => array($local => array()));
					}
				}
			}
		}

		// add all indexes
		if (isset($options['indexes']) && ! empty($options['indexes'])) {
			foreach($options['indexes'] as $index => $definition) {
				$queryFields .= ', ' . $this->getIndexDeclaration($index, $definition);
			}
		}

		// attach all primary keys
		if (isset($options['primary']) && ! empty($options['primary'])) {
			$keyColumns = array_values($options['primary']);
			$keyColumns = array_map(array($this->conn, 'quoteIdentifier'), $keyColumns);
			$queryFields .= ', PRIMARY KEY(' . implode(', ', $keyColumns) . ')';
		}

		$query = 'CREATE TABLE ' . $this->conn->quoteIdentifier($name, true) . ' (' . $queryFields . ')';

		$optionStrings = array();

		if (isset($options['comment'])) {
			$optionStrings['comment'] = 'COMMENT = ' . $this->conn->quote($options['comment'], 'text');
		}
		if (isset($options['charset'])) {
			$optionStrings['charset'] = 'DEFAULT CHARACTER SET ' . $options['charset'];
		}
		if (isset($options['collate'])) {
			$optionStrings['collate'] = 'COLLATE ' . $options['collate'];
		}

		$type = false;

		// get the type of the table
		if (isset($options['type'])) {
			$type = $options['type'];
		} else {
			$type = $this->conn->getAttribute(Doctrine_Core::ATTR_DEFAULT_TABLE_TYPE);
		}

		if ($type) {
			$optionStrings[] = 'ENGINE = ' . $type;
		}

		if ( ! empty($optionStrings)) {
			$query.= ' '.implode(' ', $optionStrings);
		}
		$sql[] = $query;

		if (isset($options['foreignKeys'])) {

			foreach ((array) $options['foreignKeys'] as $k => $definition) {
				if (is_array($definition)) {
					$sql[] = $this->createForeignKeySql($name, $definition);
				}
			}
		}
		return $sql;
	}

	/**
	 * Obtain DBMS specific SQL code portion needed to declare a generic type
	 * field to be used in statements like CREATE TABLE.
	 *
	 * @param string $name   name the field to be declared.
	 * @param array  $field  associative array with the name of the properties
	 *      of the field being declared as array indexes. Currently, the types
	 *      of supported field properties are as follows:
	 *
	 *      length
	 *          Integer value that determines the maximum length of the text
	 *          field. If this argument is missing the field should be
	 *          declared to have the longest length allowed by the DBMS.
	 *
	 *      default
	 *          Text value to be used as default for this field.
	 *
	 *      notnull
	 *          Boolean flag that indicates whether this field is constrained
	 *          to not be set to null.
	 *      charset
	 *          Text value with the default CHARACTER SET for this field.
	 *      collation
	 *          Text value with the default COLLATION for this field.
	 *      unique
	 *          unique constraint
	 *      check
	 *          column check constraint
	 *
	 * @return string  DBMS specific SQL code portion that should be used to
	 *      declare the specified field.
	 */
	public function getDeclaration($name, array $field)
	{

		$default   = $this->getDefaultFieldDeclaration($field);

		$charset   = (isset($field['charset']) && $field['charset']) ?
                    ' ' . $this->getCharsetFieldDeclaration($field['charset']) : '';

		$collation = (isset($field['collation']) && $field['collation']) ?
                    ' ' . $this->getCollationFieldDeclaration($field['collation']) : '';

		$notnull   = (isset($field['notnull']) && $field['notnull']) ? ' NOT NULL' : '';

		$unique    = (isset($field['unique']) && $field['unique']) ?
                    ' ' . $this->getUniqueFieldDeclaration() : '';

		$check     = (isset($field['check']) && $field['check']) ?
                    ' ' . $field['check'] : '';

		$comment   = (isset($field['comment']) && $field['comment']) ?
                    " COMMENT '" . $field['comment'] . "'" : '';

		$method = 'get' . $field['type'] . 'Declaration';

		try {
			if (method_exists($this->conn->dataDict, $method)) {
				return $this->conn->dataDict->$method($name, $field);
			} else {
				$dec = $this->conn->dataDict->getNativeDeclaration($field);
			}

			return $this->conn->quoteIdentifier($name, true)
			. ' ' . $dec . $charset . $default . $notnull . $comment . $unique . $check . $collation;
		} catch (Exception $e) {
			throw new Doctrine_Exception('Around field ' . $name . ': ' . $e->getMessage() . "\n\n" . $e->getTraceAsString() . "\n\n");
		}
	}

	/**
	 * alter an existing table
	 *
	 * @param string $name         name of the table that is intended to be changed.
	 * @param array $changes     associative array that contains the details of each type
	 *                             of change that is intended to be performed. The types of
	 *                             changes that are currently supported are defined as follows:
	 *
	 *                             name
	 *
	 *                                New name for the table.
	 *
	 *                            add
	 *
	 *                                Associative array with the names of fields to be added as
	 *                                 indexes of the array. The value of each entry of the array
	 *                                 should be set to another associative array with the properties
	 *                                 of the fields to be added. The properties of the fields should
	 *                                 be the same as defined by the Metabase parser.
	 *
	 *
	 *                            remove
	 *
	 *                                Associative array with the names of fields to be removed as indexes
	 *                                 of the array. Currently the values assigned to each entry are ignored.
	 *                                 An empty array should be used for future compatibility.
	 *
	 *                            rename
	 *
	 *                                Associative array with the names of fields to be renamed as indexes
	 *                                 of the array. The value of each entry of the array should be set to
	 *                                 another associative array with the entry named name with the new
	 *                                 field name and the entry named Declaration that is expected to contain
	 *                                 the portion of the field declaration already in DBMS specific SQL code
	 *                                 as it is used in the CREATE TABLE statement.
	 *
	 *                            change
	 *
	 *                                Associative array with the names of the fields to be changed as indexes
	 *                                 of the array. Keep in mind that if it is intended to change either the
	 *                                 name of a field and any other properties, the change array entries
	 *                                 should have the new names of the fields as array indexes.
	 *
	 *                                The value of each entry of the array should be set to another associative
	 *                                 array with the properties of the fields to that are meant to be changed as
	 *                                 array entries. These entries should be assigned to the new values of the
	 *                                 respective properties. The properties of the fields should be the same
	 *                                 as defined by the Metabase parser.
	 *
	 *                            Example
	 *                                array(
	 *                                    'name' => 'userlist',
	 *                                    'add' => array(
	 *                                        'quota' => array(
	 *                                            'type' => 'integer',
	 *                                            'unsigned' => 1
	 *                                        )
	 *                                    ),
	 *                                    'remove' => array(
	 *                                        'file_limit' => array(),
	 *                                        'time_limit' => array()
	 *                                    ),
	 *                                    'change' => array(
	 *                                        'name' => array(
	 *                                            'length' => '20',
	 *                                            'definition' => array(
	 *                                                'type' => 'text',
	 *                                                'length' => 20,
	 *                                            ),
	 *                                        )
	 *                                    ),
	 *                                    'rename' => array(
	 *                                        'sex' => array(
	 *                                            'name' => 'gender',
	 *                                            'definition' => array(
	 *                                                'type' => 'text',
	 *                                                'length' => 1,
	 *                                                'default' => 'M',
	 *                                            ),
	 *                                        )
	 *                                    )
	 *                                )
	 *
	 * @param boolean $check     indicates whether the function should just check if the DBMS driver
	 *                           can perform the requested table alterations if the value is true or
	 *                           actually perform them otherwise.
	 * @return boolean
	 */
	public function alterTableSql($name, array $changes, $check = false)
	{
		if ( ! $name) {
			throw new Doctrine_Export_Exception('no valid table name specified');
		}
		foreach ($changes as $changeName => $change) {
			switch ($changeName) {
				case 'add':
				case 'remove':
				case 'change':
				case 'rename':
				case 'name':
					break;
				default:
					throw new Doctrine_Export_Exception('change type "' . $changeName . '" not yet supported');
			}
		}

		if ($check) {
			return true;
		}

		$query = '';
		if ( ! empty($changes['name'])) {
			$change_name = $this->conn->quoteIdentifier($changes['name']);
			$query .= 'RENAME TO ' . $change_name;
		}

		if ( ! empty($changes['add']) && is_array($changes['add'])) {
			foreach ($changes['add'] as $fieldName => $field) {
				if ($query) {
					$query.= ', ';
				}
				$query.= 'ADD ' . $this->getDeclaration($fieldName, $field);
			}
		}

		if ( ! empty($changes['remove']) && is_array($changes['remove'])) {
			foreach ($changes['remove'] as $fieldName => $field) {
				if ($query) {
					$query .= ', ';
				}
				$fieldName = $this->conn->quoteIdentifier($fieldName);
				$query .= 'DROP ' . $fieldName;
			}
		}

		$rename = array();
		if ( ! empty($changes['rename']) && is_array($changes['rename'])) {
			foreach ($changes['rename'] as $fieldName => $field) {
				$rename[$field['name']] = $fieldName;
			}
		}

		if ( ! empty($changes['change']) && is_array($changes['change'])) {
			foreach ($changes['change'] as $fieldName => $field) {
				if ($query) {
					$query.= ', ';
				}
				if (isset($rename[$fieldName])) {
					$oldFieldName = $rename[$fieldName];
					unset($rename[$fieldName]);
				} else {
					$oldFieldName = $fieldName;
				}
				$oldFieldName = $this->conn->quoteIdentifier($oldFieldName, true);
				$query .= 'CHANGE ' . $oldFieldName . ' '
				. $this->getDeclaration($fieldName, $field['definition']);
			}
		}

		if ( ! empty($rename) && is_array($rename)) {
			foreach ($rename as $renameName => $renamedField) {
				if ($query) {
					$query.= ', ';
				}
				$field = $changes['rename'][$renamedField];
				$renamedField = $this->conn->quoteIdentifier($renamedField, true);
				$query .= 'CHANGE ' . $renamedField . ' '
				. $this->getDeclaration($field['name'], $field['definition']);
			}
		}

		if ( ! $query) {
			return false;
		}

		$name = $this->conn->quoteIdentifier($name, true);

		return 'ALTER TABLE ' . $name . ' ' . $query;
	}

	/**
	 * create sequence
	 *
	 * @param string    $sequenceName name of the sequence to be created
	 * @param string    $start        start value of the sequence; default is 1
	 * @param array     $options  An associative array of table options:
	 *                          array(
	 *                              'comment' => 'Foo',
	 *                              'charset' => 'utf8',
	 *                              'collate' => 'utf8_unicode_ci',
	 *                              'type'    => 'innodb',
	 *                          );
	 * @return boolean
	 */
	public function createSequence($sequenceName, $start = 1, array $options = array())
	{
		$sequenceName   = $this->conn->quoteIdentifier($sequenceName, true);
		$seqcolName     = $this->conn->quoteIdentifier($this->conn->getAttribute(Doctrine_Core::ATTR_SEQCOL_NAME), true);

		$optionsStrings = array();

		if (isset($options['comment']) && ! empty($options['comment'])) {
			$optionsStrings['comment'] = 'COMMENT = ' . $this->conn->quote($options['comment'], 'string');
		}

		if (isset($options['charset']) && ! empty($options['charset'])) {
			$optionsStrings['charset'] = 'DEFAULT CHARACTER SET ' . $options['charset'];

			if (isset($options['collate'])) {
				$optionsStrings['charset'] .= ' COLLATE ' . $options['collate'];
			}
		}

		$type = false;

		if (isset($options['type'])) {
			$type = $options['type'];
		} else {
			$type = $this->conn->getAttribute(Doctrine_Core::ATTR_DEFAULT_TABLE_TYPE);
		}
		if ($type) {
			$optionsStrings[] = 'ENGINE = ' . $type;
		}


		try {
			$query  = 'CREATE TABLE ' . $sequenceName
			. ' (' . $seqcolName . ' BIGINT NOT NULL AUTO_INCREMENT, PRIMARY KEY ('
			. $seqcolName . ')) ' . implode($optionsStrings, ' ');

			$res    = $this->conn->exec($query);
		} catch(Doctrine_Connection_Exception $e) {
			throw new Doctrine_Export_Exception('could not create sequence table');
		}

		if ($start == 1 && $res == 1)
		return true;

		$query  = 'INSERT INTO ' . $sequenceName
		. ' (' . $seqcolName . ') VALUES (' . ($start - 1) . ')';

		$res    = $this->conn->exec($query);

		if ($res == 1)
		return true;

		// Handle error
		try {
			$result = $this->conn->exec('DROP TABLE ' . $sequenceName);
		} catch(Doctrine_Connection_Exception $e) {
			throw new Doctrine_Export_Exception('could not drop inconsistent sequence table');
		}


	}

	/**
	 * Get the stucture of a field into an array
	 *
	 * @author Leoncx
	 * @param string    $table         name of the table on which the index is to be created
	 * @param string    $name          name of the index to be created
	 * @param array     $definition    associative array that defines properties of the index to be created.
	 *                                 Currently, only one property named FIELDS is supported. This property
	 *                                 is also an associative with the names of the index fields as array
	 *                                 indexes. Each entry of this array is set to another type of associative
	 *                                 array that specifies properties of the index that are specific to
	 *                                 each field.
	 *
	 *                                 Currently, only the sorting property is supported. It should be used
	 *                                 to define the sorting direction of the index. It may be set to either
	 *                                 ascending or descending.
	 *
	 *                                 Not all DBMS support index sorting direction configuration. The DBMS
	 *                                 drivers of those that do not support it ignore this property. Use the
	 *                                 function supports() to determine whether the DBMS driver can manage indexes.
	 *
	 *                                 Example
	 *                                    array(
	 *                                        'fields' => array(
	 *                                            'user_name' => array(
	 *                                                'sorting' => 'ASC'
	 *                                                'length' => 10
	 *                                            ),
	 *                                            'last_login' => array()
	 *                                        )
	 *                                    )
	 * @throws PDOException
	 * @return void
	 */
	public function createIndexSql($table, $name, array $definition)
	{
		$table  = $table;
		$table  = $this->conn->quoteIdentifier($table, true);

		$name   = $this->conn->formatter->getIndexName($name);
		$name   = $this->conn->quoteIdentifier($name);
		$type   = '';
		if (isset($definition['type'])) {
			switch (strtolower($definition['type'])) {
				case 'fulltext':
				case 'unique':
					$type = strtoupper($definition['type']) . ' ';
					break;
				default:
					throw new Doctrine_Export_Exception(
                        'Unknown type ' . $definition['type'] . ' for index ' . $name . ' in table ' . $table
					);
			}
		}
		$query  = 'CREATE ' . $type . 'INDEX ' . $name . ' ON ' . $table;
		$query .= ' (' . $this->getIndexFieldDeclarationList($definition['fields']) . ')';

		return $query;
	}

	/**
	 * getDefaultDeclaration
	 * Obtain DBMS specific SQL code portion needed to set a default value
	 * declaration to be used in statements like CREATE TABLE.
	 *
	 * @param array $field      field definition array
	 * @return string           DBMS specific SQL code portion needed to set a default value
	 */
	public function getDefaultFieldDeclaration($field)
	{
		$default = '';
		if (isset($field['default']) && ( ! isset($field['length']) || $field['length'] <= 255)) {
			if ($field['default'] === '') {
				$field['default'] = empty($field['notnull'])
				? null : $this->valid_default_values[$field['type']];

				if ($field['default'] === ''
				&& ($this->conn->getAttribute(Doctrine_Core::ATTR_PORTABILITY) & Doctrine_Core::PORTABILITY_EMPTY_TO_NULL)
				) {
					$field['default'] = ' ';
				}
			}

			// Proposed patch:
			if ($field['type'] == 'enum' && $this->conn->getAttribute(Doctrine_Core::ATTR_USE_NATIVE_ENUM)) {
				$fieldType = 'varchar';
			} else {
				$fieldType = $field['type'];
			}

			$default = ' DEFAULT ' . (is_null($field['default'])
			? 'NULL'
			: $this->conn->quote($field['default'], $fieldType));
			//$default = ' DEFAULT ' . $this->conn->quote($field['default'], $field['type']);
		}

		return $default;
	}

	/**
	 * Obtain DBMS specific SQL code portion needed to set an index
	 * declaration to be used in statements like CREATE TABLE.
	 *
	 * @param string $charset       name of the index
	 * @param array $definition     index definition
	 * @return string  DBMS specific SQL code portion needed to set an index
	 */
	public function getIndexDeclaration($name, array $definition)
	{
		$name   = $this->conn->formatter->getIndexName($name);
		$type   = '';
		if (isset($definition['type'])) {
			switch (strtolower($definition['type'])) {
				case 'fulltext':
				case 'unique':
					$type = strtoupper($definition['type']) . ' ';
					break;
				default:
					throw new Doctrine_Export_Exception(
                        'Unknown type ' . $definition['type'] . ' for index ' . $name
					);
			}
		}

		if ( ! isset($definition['fields'])) {
			throw new Doctrine_Export_Exception('No columns given for index ' . $name);
		}
		if ( ! is_array($definition['fields'])) {
			$definition['fields'] = array($definition['fields']);
		}

		$query = $type . 'INDEX ' . $this->conn->quoteIdentifier($name);

		$query .= ' (' . $this->getIndexFieldDeclarationList($definition['fields']) . ')';

		return $query;
	}

	/**
	 * getIndexFieldDeclarationList
	 * Obtain DBMS specific SQL code portion needed to set an index
	 * declaration to be used in statements like CREATE TABLE.
	 *
	 * @return string
	 */
	public function getIndexFieldDeclarationList(array $fields)
	{
		$declFields = array();

		foreach ($fields as $fieldName => $field) {
			$fieldString = $this->conn->quoteIdentifier($fieldName);

			if (is_array($field)) {
				if (isset($field['length'])) {
					$fieldString .= '(' . $field['length'] . ')';
				}

				if (isset($field['sorting'])) {
					$sort = strtoupper($field['sorting']);
					switch ($sort) {
						case 'ASC':
						case 'DESC':
							$fieldString .= ' ' . $sort;
							break;
						default:
							throw new Doctrine_Export_Exception('Unknown index sorting option given.');
					}
				}
			} else {
				$fieldString = $this->conn->quoteIdentifier($field);
			}
			$declFields[] = $fieldString;
		}
		return implode(', ', $declFields);
	}

	/**
	 * getAdvancedForeignKeyOptions
	 * Return the FOREIGN KEY query section dealing with non-standard options
	 * as MATCH, INITIALLY DEFERRED, ON UPDATE, ...
	 *
	 * @param array $definition
	 * @return string
	 */
	public function getAdvancedForeignKeyOptions(array $definition)
	{
		$query = '';
		if ( ! empty($definition['match'])) {
			$query .= ' MATCH ' . $definition['match'];
		}
		if ( ! empty($definition['onUpdate'])) {
			$query .= ' ON UPDATE ' . $this->getForeignKeyReferentialAction($definition['onUpdate']);
		}
		if ( ! empty($definition['onDelete'])) {
			$query .= ' ON DELETE ' . $this->getForeignKeyReferentialAction($definition['onDelete']);
		}
		return $query;
	}

	/**
	 * drop existing index
	 *
	 * @param string    $table          name of table that should be used in method
	 * @param string    $name           name of the index to be dropped
	 * @return void
	 */
	public function dropIndexSql($table, $name)
	{
		$table  = $this->conn->quoteIdentifier($table, true);
		$name   = $this->conn->quoteIdentifier($this->conn->formatter->getIndexName($name), true);
		return 'DROP INDEX ' . $name . ' ON ' . $table;
	}

	/**
	 * dropTable
	 *
	 * @param string    $table          name of table that should be dropped from the database
	 * @throws PDOException
	 * @return void
	 */
	public function dropTableSql($table)
	{
		$table  = $this->conn->quoteIdentifier($table, true);
		return 'DROP TABLE ' . $table;
	}

	/**
	 * drop existing foreign key
	 *
	 * @param string    $table        name of table that should be used in method
	 * @param string    $name         name of the foreign key to be dropped
	 * @return void
	 */
	public function dropForeignKey($table, $name)
	{
		$table = $this->conn->quoteIdentifier($table);
		$name  = $this->conn->quoteIdentifier($name);

		return $this->conn->exec('ALTER TABLE ' . $table . ' DROP FOREIGN KEY ' . $name);
	}
}